The use of high energy laser beams to produce photochemical reactions is known. For example, copending application Ser. No. 302,348 filed Sept. 15, 1981 entitled "Photochemical Reaction Cavity" by the same inventor describes a cavity for interacting ultraviolet and infrared radiation with gas molecules as part of a photochemical process. To achieve high efficiency in such a process, the laser beams must be generated and directed into the cavity with a minimum of energy loss. The present invention is directed to a beam generating module which delivers multiple beams of more than one frequency to such a cavity or other target in a highly efficient, optically accurate, and reliable manner.